Because cancer is a leading cause of death in postmenopausal women, detailed epidemiological investigations are warranted to identify etiologic factors, including potentially modifiable risk factors, for cancer and to better understand health issues for cancer survivors. The Iowa Women's Health Study (IWHS) recruited a population-based cohort of 41,836 Iowa women, aged 55-69 years in 1986, to determine whether diet, body fat distribution, and other risk factors were related to cancer incidence. Exposure and lifestyle information was collected in a baseline mailed survey and five follow-up surveys in 1987, 1989, 1992, 1997, and 2004. Cancer incidence and mortality have been ascertained since 1986 by linkage with the Iowa Cancer Registry, a SEER site, and the National Death Index. The project has been extremely productive, with nearly 200 publications, and key findings related to body fat distribution, diet, and other risk factors for cancer. With the existing wealth of information on this large cohort of women, we propose in this 5-year renewal to extend follow-up for cancer incidence and mortality through 22 years. Further IWHS follow-up is expected to yield a total of at least 9,723 incident cancers and 15,756 deaths. We also propose linkage of the IWHS cohort to the Medicare database through 2004, to retrospectively identify, for women 65+, new exposures, new cancer-relevant endpoints, and outcomes after cancer. This linkage will allow us to test hypotheses in six broad areas: a) dietary risk factors for common cancers;b) non-dietary risk factors for common cancers;c) risk factors for uncommon cancers;d) cancer outcomes;e) risk factors for cancers not previously available from SEER;and f) the epidemiology of high risk or premalignant conditions. The proposed extension of IWHS will provide new information on the risk and outcomes of cancer in older women. The incremental cost needed to combine Medicare data with IWHS data is relatively small, yet the new opportunities afforded by this linkage are substantial. With this progressive approach, continued funding of the IWHS should prove to be of value in the control of this major public health problem.